A quantum dot is a material having a nanocrystal structure and consists of several hundred to several thousands of atoms. As the quantum dot has an extremely small size, it leads to quantum confinement. The quantum confinement effect refers to the phenomenon in which the energy band gap of a material increases when the material has a size measured in nanoscale or a smaller measurement scale. As a result, when the light having a wavelength with energy higher than the energy band gap strikes the surface of a quantum dot, the quantum dot absorbs the light, becomes excited, emits a light of a specific wavelength and then returns to the ground state. The wavelength of the emitted light is dependent upon the energy corresponding to the energy band gap.
Generally, the shorter the wavelength of the emitted light, the smaller the particle size of the quantum dot; and the longer the wavelength of the emitted light, the larger the particle size of the quantum dot. This is the electrical/optical characteristic peculiar to the quantum dot, which is different from existing semiconductor materials. It is therefore possible to realize a desired light-emitting characteristic by controlling the size and composition of the quantum dot.